A metal CVT belt for high load transmission used in a continuously variable transmission (CVT) is formed of belt stacks each consisting of circular belts, the belt stacks being arranged in the width direction of the belt. The belt stacks are each locked and fastened with a plurality of blocks (elements). For example, as shown in FIG. 18a, circular belts a, a, . . . are stacked to form a stack b, and such stacks b, b are fitted in a plurality of blocks c, c, . . . to form a CVT belt d. The circular belt a is formed as follows. Edges of metal plates are welded to form a cylindrical metal drum of the thin plates. The metal drum is entirely subjected to heat treatment (solution treatment) so as to conform the welded portion and the base material to each other. Thereafter, the metal drum is sheared with an external roll cutter abutted against an internal roll cutter disposed inside the cylinder. The circular belts thus cut are subjected to barrel polishing in a final step. Barrel polishing involves putting a polished member (work) and a polisher (medium) in a barrel (container) so as to remove burrs by the relative friction of the work and the medium caused by the motion of the barrel, or to perform surface processing, such as providing a corner with an R.
During the cutting by the roll cutters, a burr a1 (outwardly stretched projection) or a droop (inwardly stretched depression in the width direction of the belt) are often caused, as shown in FIG. 18b. In order to remove such burr or droop, the aforementioned barrel polishing is performed. Further, an oxide film a2 with a thickness of approximately 1 μm, which is formed on the surface of the belt during solution treatment and that prevents the nitriding of the belt surface, can also be removed by barrel polishing. Barrel polishing can be further used for providing a corner of the belt edge surface with a smooth curve (radiusing).
As mentioned above, during the conventional CVT belt formation process, barrel polishing is performed to remove oxide films, burrs, or droops. However, such barrel polishing is not capable of completely removing the burrs or droops. The removal of the oxide film formed on the belt surface takes approximately one hour, resulting in decrease in the belt production efficiency. In addition, such barrel polishing produces large quantities of waste material of the medium, the disposal of which is a significant problem.
Reference 1 discloses an invention directed to a processing method for grinding the edges of a belt that does not involve the barrel polishing step. In this processing method, metal rings cut out of a metal drum are rotated in their circumferential direction, while a polishing brush, which is disposed to intersect the trajectory of the metal rings as they rotate at an incident angle of 20° to 45°, is abutted against the ring edge surface to polish the same. The polishing brush is similarly moved away from the metal rings at a withdrawal angle of 20° to 45°. These angular ranges are adopted for the following considerations. Namely, if the incident angle is less than 20°, the polishing brush would polish the internal circumferential surface of the metal rings. If the incident angle and the withdrawal angle exceeds 45°, only the tip of the side edge of the metal rings would be polished.
Patent Document 1: JP Patent Publication (Kokai) No. 2004-261882 A